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5. Which element is a metal?

(a) Se (atomic number = 34)

(b) Co (atomic number = 27)

(c) C (atomic number = 6)

(d) Br (atomic number = 35)

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Selena Adewinogo
Selena AdewinogoLv9
23 Feb 2021

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Related questions

Which of the following statements is TRUE? (a) The atomic number is the same as the mass number. (b) The atomic number is the same as the number of protons. (c) The identity of a chemical element is determined by the number of valence electrons. (d) The radius of all atoms can be measured precisely. (e) Different isotopes of an element have different atomic numbers.

Moseley established the concept of atomic number by studying X rays emitted by the elements. The X rays emitted by some of the elements have the following wavelengths:

(a) Calculate the frequency, v, of the X rays emitted by each of the elements, in Hz. (b) Plot the square root of v versus the atomic number of the element. What do you observe about the plot? (c) Explain how the plot in part (b) allowed Moseley to predict the existence of undiscovered elements. (d) Use the result from part (b) to predict the X-ray wavelength emitted by iron. (e) A particular element emits X rays with a wavelength of 0.980 ƅ. What element do you think it is?

Using the same formula, frequencies of four other elements are calculated:

Ļ…(Ca) = 8.928 Ɨ 1017 Hz

Ļ…(Zn) = 2.089 Ɨ 1018 Hz

Ļ…(Zr) = 3.81 Ɨ 1018 Hz

Ļ…(Sn) = 6.11 Ɨ 1018 Hz

b)

The plot is linear, which allows the prediction the frequencies of new elements based on the equation of the trendline.

c) Moseley could predict the existence of undiscovered elements by filling the gaps in the plot of sqrt(v) vs. atomic number. If a new frequency is observed, it could be connected with the atomic number and in this way new element could be discovered.

d) Iron has atomic number 26.

The square root of v(iron) = 5Ɨ107Ɨ(Atomic number) ā€“ 6Ɨ107 = 1.24Ɨ109

The frequency of radiation is 1.54Ɨ1018 Hz, and the corresponding wavelength is:

e) The frequency of 0.980 ƅ radiation is:

Using the graph in (b), we can calculate x if we put sqrt of v as y.

1.75Ɨ109 = 5Ɨ107Ɨ(Atomic number) ā€“ 6Ɨ107

Atomic number = 36

The unknown element is krypton, Kr.

1)What is the formula for potassiumdiamminetetrachlorovanadate(III)?

a) [KV(NH3)2Cl4]

b) K2[V(NH3)2Cl4]

c) K[V(NH3)2Cl4]

d)[KV(NH3)2]Cl4

e)K[V(NH3)2]Cl4

2. The effective atomic number (EAN) rule states thatorganometallic coordination compounds are likely to be stable if____ ?

a) the oxidation state of the metal is zero.

b) the sum of the metal valence electrons plus the electronsdonated by the ligand equals 18.

c) the ligand field splitting is small.

d)the metal has an even atomic number.

e) the metal has an odd atomic number.

3) What are the possible geometries of a metal complex with acoordination number of 4?

1. square planar

2. tetrahedral

3. octahedral

a)1 only

b) 2 only

c) 3 only

d) 1 and 2

e) 1, 2, and 3

4) Determine the number of unpaired electrons in the tetrahedralcomplex ion [Co(NH3)4]2+,

a)0

b)1

c)2

d)3

e) 4

5) Iron, _____, and sulfur form the reactive portion ofnitrogenase, a biological catalyst used by nitrogen-fixingorganisms.

a) Fe

b)Co

c)Zn

d)Cd

e) Mo

6) Which element has the highest density?

a) Zn

b)Y

c) Os

d) Fe

e) Ag

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